It is well known that ellipsometer and polarimeter systems allow determination of sample system physical and optical properties, (such as thickness, refractive index and extinction coefficient of surface films thereon), by detecting change in "Polarization State" and/or Intensity of a beam of polarized light which is caused to interact with said sample system, where Polarization State here refers to a set of values for Polarized Light Beam Orthogonal Components, (such as "S" and "P"), Magnitude Ratio, and a Phase Angle therebetween. (It is noted that "P" refers to that component which is in a plane containing the normal to a sample system and incident and/or transmitted beam(s) of polarized light, and "S" refers to that component perpendicular thereto and parallel to the surface of said sample system. It is also noted that a "full" polarization state also requires designation of an absolute value to which a magnitude ratio is referenced, and the direction of rotation of a polarized beam of light).
As a general comment it is noted that polarimetry is focused on determining full polarization states of electromagnetic radiation beams, whereas ellipsometry is focused on determining a change in a state of polarization of a beam of electromagnetic radiation because of interaction with a sample system, but both systems have as a common requirement the need for a means to polarize beams of electromagnetic radiation.
Continuing, a polarizer system for polarizing a beam of electromagnetic radiation can be as simple as a physical slit in an opaque material, or can comprise a Wire Grid, or can be a system which operates on the basis of causing unequal effects on orthogonal components of a beam of electromagnetic radiation caused to interact therewith, (ie. a Brewster Angle Polarizer System). It is well known that orthogonal components of a polarized beam of electromagnetic radiation which is caused to interact with a semiconductor substrate for instance, wherein the beam of polarized beam of electromagnetic radiation is caused to approach the semiconductor substrate at an angle of incidence of near seventy-five (75) degrees, are affected differently. The component perpendicular to the semiconductor substrate surface is reflected, while the component parallel to the semiconductor surface is mostly passed therethrough. By subjecting such a beam of electromagnetic radiation to a sequence of such interactions it is possible to produce a linearly polarized beam. Such a configuration, however, requires that a sufficiently large laterally dimensioned space be available to allow for the necessary number of stages required to sufficiently polarize a beam of electromagnetic radiation. It is also noted that polarizer systems should provide a beam of electromagnetic radiation which exits therefrom along a locus which is undeviated and undisplaced from an incident beam of electromagnetic radiation, as in use, said polarizer system is often rotated to provide various planes of polarization to a sample, system, while data is obtained.
A search of Patents provided nothing obviating of the present invention, but did turn-up some references of interest.
For instance, U.S. Pat. No. 4,221,464 to Pedinoff et al. shows a Double Plate Brewster Angle Polarizer (10) (12) which serves to avoid back reflections, which is combined with a Wire Grid Polarizer (28) present on Plate (14). A purpose of the invention is to increase the extinction coefficient of the Wire Grid Polarizer, by combining it with the Double Plate Brewster Angle Polarizer (10) (12).
A U.S. Pat. No. 5,177,635 to Keilmann, shows an Infrared Polarizer Structure of patterned metal strips on a transparent material, but does not suggest a dual polarizer arrangement.
A U.S. Pat. No. 4,961,634 to Chipman et al., shows two polarizers made of CdS and CdSe respectively, in series.
A U.S. Pat. No. 2,815,452 to Mertz, shows multiple Wire Grids oriented at angles with respect to one another. The system is an Interferometer in which said one said Wire Grid is rotated with respect to another.
A U.S. Pat. No. 3,439,968 to Hanson, shows an Infrared Brewster Angle Polarizer.
A U.S. Pat. No. 3,428,388 to Kuebler et al., shows a UV "Biotite" based Brewster Angle Polarizer.
A U.S. Pat. No. 5,187,611 to White eta l., shows a system which illuminates an object while avoiding reflection and glare.
U.S. Pat. Nos. 4,733,926 to Title; 5,548,427 to May and 5,402,260 to Tsuneda et al. were also identified.
Also, a reference titled "ELLIPSOMETRY AND POLARIZED LIGHT", by Azzam and Bashara, North-Holand, 1977, is incorporated by reference into this Disclosure for the purpose of providing general information regarding sample analysis systems utilizing electromagnetic beams, ellipsometry, polarimetry and fundamentals of electromagnetic beams.
A laterally compact polarizer system which would provide a high extinction ration, (ie. a large difference in the magnitude between orthogonal components in a beam of electromagnetic radiation exiting therefrom), and provide a beam of electromagnetic radiation which exits therefrom along a locus which is undeviated and undisplaced from an incident beam of electromagnetic radiation, would provide utility in many applications. The present invention provides such a system, and method of its use.